CL-USER(1): (truename "sys:opengl;")
#P"/Applications/AllegroCL/opengl/"
CL-USER(2): (truename "sys:opengl;macosx-2.0;")
Error: There is no file named sys:opengl;macosx-2.0;
  [condition type: FILE-ERROR]

Restart actions (select using :continue):
 0: Return to Top Level (an "abort" restart).
 1: Abort entirely from this (lisp) process.
[1] CL-USER(3): :exit
; Exiting
DHX-Computer:~ Francois$ ls /Applications/AllegroCL/opengl/macosx-2.0/
opengl.cl